[Terrapreta] Planning a small TP trial

[Bear Kaufmann]

Hi all,

I will be conducting a small terra preta trial as a final project for a 
course in food and agriculture that I am currently taking.
I'll give a short synopsis of the plan:
    Radish will be used due to growth time constraints.
    Soil composition will be varied by percentage composition across 
three factors:
       Potting Mix (nutrient source, with manufacturer composition noted)
       Horticultural Sand (as a rough proxy for leached tropical soils)
       Char (planning on using available English Walnut hull char, 
crushed to 1/8" mesh)
    The above factors will be distributed in a three factor graph akin 
to the soil texture classification chart (see 
http://en.wikipedia.org/wiki/Image:SoilTextureTriangle.jpg):
       Each edge will be subdivided into 7 percentages (0-100% with ~16% 
increments)
       The above gives 28 trials, each trial will have three individual pots
    Pots will be assigned a number randomly and arranged in numerical 
order in a rectangular grid
    Plants will be grown outdoors in coir fiber pots and watered on a timer
    At maturity (~30 days), plant wet weight will be measured

Jim Mason has suggested a trial to test the effects of particle size on 
growth, which I plan to implement (hold a 1 part mix/sand/char 
composition constant and varying particle size).
Bernie Lenhoff has suggested fungal inoculation of the char. Are there 
any easily available sources of beneficial fungi to mix with the char 
that won't directly effect the nutrient content of the char?

I'm planning on mixing compositions and planting this weekend.

If anyone has any recommendations for small alterations to the 
methodology that would make the trial more useful, let me know.

Thanks,
Bear Kaufmann